This study is designed to characterize the central actions of drugs on intestinal motility and intestinal propulsion. Studies of intestinal motility will be performed on unanesthetized animals surgically implanted with extracellular electrodes and extraluminal force transducers on the small intestine. Central and peripheral emetic agents, as well as reserpine, will be administered either systemically or into a lateral cerebral ventricle of the brain while myoelectrical or contractile activities at several loci along the small intestine are monitored simultaneously. Centrally mediated patterns of intestinal motility associated with drug-induced vomiting and diarrhea will be defined, and the efferent nerve pathway(s) determine. Central and/or peripheral effects of drug which increase (reserpine) or decrease (narcotic agents) intestinal propulsion will be investigated using the unanesthetized rat. Intestinal propulsion will be determined by measuring the progression through the intestine of an intraduodenally administered radioactive marker. Drugs will be administered systemically or by intracerebroventricular injection. Modification of central actions of reserpine and narcotic agents on intestinal propulsion will be attempted by central or peripheral administration of specific receptor antagonists, and by surgical transection of the extrinsic nerve supply to the intestine. The results of this study will increase our understanding of drugs which affect intestinal function therapeutically or as a side-effect. In addition, the results will improve our knowldege of the central nervous system control of intestinal function.